EP 1 370 773 B1 discloses a directional control valve for controlling the pressure and flow of hydraulic oil to and from useful ports of at least one consumer. The pressure and flow can be controlled by a sliding plunger as the control device which can be moved in a spool bore and which can be activated by at least one drive, and by ring channels which are dynamically connected to it as part of the fluid port arrangement. At the center point of symmetry on one axis of symmetry, a tank port ring channel R and other ring channels are symmetrically located on both sides and are components of the fluid port arrangement of the directional control valve. The sliding plunger as a component of this control device is activated by an activation unit which stipulates the respective control pressure on the opposite control sides of the sliding plunger. The activation unit includes a differential cylinder which is located on one side of the actual valve housing, which induces activation for both stroke directions of the optionally two-part sliding plunger, and which constitutes a separate component.
WO 2006/005496 A1 discloses a generic valve device, in particular in the form of a valve arrangement of a lifting mechanism. The known solution is used to activate a double-acting lifting mechanism or the attachment device of an agricultural vehicle with a continuously adjustable directional control valve which forms a metering throttle and to which an individual pressure compensator is assigned. Via the pressure compensator a volumetric flow of hydraulic fluid flows to a working port A, B. The hydraulic fluid flows back via another working port A, B flowing out via a directional control valve to a low pressure port or tank port T. A pressure limitation valve is located in a working line between the directional control valve and the working port A, B.
The pressure limitation valve is preferably proportionally adjustable so that the pressure in the working line can be limited to different maximum values depending on the different operating states. To trigger the control device in the form of the sliding plunger of the indicated directional control valve, a control or pilot valve is used whose fluid-carrying output ports are connected to two control lines which are each routed to the face-side control spaces of the directional control valve. One control line leading to the control chamber side of the directional control valve, which side is farther away, is designed, coming from the control or pilot valve, as a long connecting bore which is very thin in cross section, for which suitable drilling tools must be made available. A solution comparable thereto is also shown in DE 603 04 663 T2.